1. Field of the Invention
The present invention relates to a novel cosmetic composition and, particularly, to an emulsion type cosmetic composition.
2. Description of the Prior Art
Emulsion type cosmetics such as creams or skin lotions, are classified into two types, namely an oil in water (O/W) type emulsion wherein an oil component as the cosmetic base material is dispersed in water with use of an emulsifier and a water in oil (W/O) type emulsion wherein water is dispersed in the oil component.
As emulsifiers for stabilizing such emulsion systems, there have mainly been used non-ionic surface active agents such as polyoxyethylene alkyl ether, an oxyethylene oxypropylene block copolymer, a sorbitan fatty acid ester, and a polyoxyethylene sorbitan fatty acid ester. However, these emulsifiers cause irritation to the skin and they are accordingly not necessarily satisfactory.
On the other hand, it is known that cholesterol having a unique structure with a hydroxyl group at the C-3 position and a double bond at the C-5 and C-6 positions, exhibits surface activity. Cholesterol is widely distributed in nature and, especially in the animal body, it is distributed in almost all systems not to mention epithelial fat, and it plays an important role in physiological processes. Further, cholesterol has a mild penetration property and an activity to keep the skin surface in a moist condition , and it gives little irritation to the skin. Because of these outstanding characteristics suitable for a material for cosmetics, it is used for the production of cosmetics.
There have recently been studies on the reformation of cholesterol in an attempt to obtain a derivative useful as a material for cosmetics. For instance, a technique is reported wherein an alkylene oxide such as ethylene oxide or propylene oxide, is added to cholesterol to improve the hydrophilic property and the cholesterol derivative thus produced are used as an emulsifier for cosmetics (Japanese Patent Publication No. 28501 of 1975).
However, most of the above mentioned cholesterol derivatives have a high melting point and are normally solid at room temperature. Accordingly, it is necessary to take special measures when they are used, and in some cases, the amount of use and the area for application is restricted.
A need therefore continues to exist for emulsifiers suitable for use in cosmetics which are liquid at room temperature and give little irritation to the skin.